Downhill mountainbikes are popular conversions. They are designed with high speeds and impacts in mind. The cost may be prohibitive to many DIYers though.
For high speed (50km/h), adequate tires are also necessary. E50 rated tires are now widely available that can handle the speeds and loads.
You're much more likely to target a "trail" full suspension mountain bike or fixed tail bike. You'll have a lot more cost options and they're more suitable for a commuting purpose, they'd still have plenty of travel and braking compared to a standard commuter or utility E-bike. As a note, my mid-level trail bike came with a better set of brakes then my high end cargo hauler e-bike which weighed about 10 times as much.
Long seatposts that bring you up to a typical height are fine. The suspension is doing the work, no need to leave the saddle.
I wouldn't recommend converting a road bike as they are more fragile.
I’d guess e-scooter/moped is next best thing tho parking is an issue in some places.
A "cheap" bike is just a rigid frame with rigid forks.
A fat tire can stand in for a shock, but "cheap" bikes don't usually fit 3" of rubber either.
[1] https://elettrica-bike.it/en/product/fat-bike-vulcano-s-tipe...
I don’t see any ebikes being sold without at least a 50mm front shock. The added weight of the battery+motor makes it essential
Ahhhh I think I understand - it's a "speedbike" right? So only for driving on roads like a car, so there's no question of forest tracks or gravel walkways.
Yep, they're both commuter/cruiser type bikes, so probably not best offroad.
Both have the top end Bosch Class 3 motor, so they're usually against the rules on trails in my area.
If you ride it like a bicycle and try to avoid potholes and curbs, simpler designs work great.
My assumption is that people buy them since they are a touch more comfortable than a full rigid bike frame.